More precisely, the invention relates to improvements to headlights of this type in which the smooth surface of the reflector is also designed to impart considerable width to the beam without help from the closure glass. This avoids the well-known optical defects that appear, in particular when a large amount of lateral deflection is required of a closure glass which slopes relative to the vertical.
Headlights of this type are described in our earlier French patent application published under the number 2 609 148.
However, in all these prior headlights, the deflection imparted to the light rays reflected by the reflector always occurs in a horizontal plane. In particular, this means that for a European type dipped headlight, the rays which normally define the sloping half cut-off of this type of beam are moved away from the half cut-off by such deflection. In practice, this gives rise to a horizontal half cut-off which is well defined over a wide width, whereas the half cut-off which slopes relative to the horizontal is defined only over a very narrow width. This is clearly illustrated in FIG. 13 of the above-mentioned patent application where it can be seen that the sloping half cut-off is extended to the right merely by an extension of the horizontal half cut-off on the left.
In addition, in the headlights described in said patent application, the width of the beam is obtained essentially by the design of the central region of the complex reflector. This is not always compatible with having a direct light mask disposed in front of the lamp. Although it gives rise to a beam of the required width by reinforcing the convergence of the rays reflected on the back, a large proportion of these rays are then intercepted by the mask and do not contribute to the beam. Light output is thus reduced.
The present invention seeks to mitigate the drawbacks of the prior art and to provide a headlight having a cut-off beam of the above-mentioned type in which, solely by an appropriate design of the reflector which continues to have an essentially continuous and smooth surface, a substantial increase is obtained in beam width not only horizontally, but also, where appropriate, essentially parallel to the sloping portion of the cut-off, and in particular along the upwardly-directed lift angle of the cut-off along the sloping half cut-off of a standardized European dipped beam.
A secondary object of the present invention, when the lamp used includes a direct light mask placed in front of the lamp, is to minimize the quantity of light which is directed towards the mask after being reflected on the reflector, and which therefore does not contribute to forming the beam.